EP0194790B1

EP0194790B1 - Helical scan type magnetic recording and reproducing apparatus

Info

Publication number: EP0194790B1
Application number: EP86301471A
Authority: EP
Inventors: Hirota Akira; Matsuo Yasutoshi
Original assignee: Victor Company of Japan Ltd
Current assignee: Victor Company of Japan Ltd
Priority date: 1985-02-28
Filing date: 1986-02-28
Publication date: 1990-12-05
Also published as: US4757391A; DE194790T1; EP0194790A1; DE3675960D1

Description

The present invention generally relates to helical scan type magnetic recording and reproducing apparatuses for forming tracks which are mutually separated in a width direction of a tape, and more particularly to a magnetic recording and reproducing apparatus which records three kinds of signals constituting a color video signal on a plurality of tracks which are mutually separated in the tape width direction by use of a plurality of rotary heads which simultaneously and independently form the plurality of tracks, and obtains at the time of a reproduction a picture having a satisfactory quality and having only an extremely small time base deviation.
A helical scan type magnetic recording and reproducing apparatus (VTR) which uses a magnetic tape having a width of inch is presently used in various fields. However, in the VTR for home use, the frequency band in which the recording and reproduction can be performed is relatively narrow. For this reason, in the VTR for home use, a luminance signal separated from a color video signal is frequency-modulated and a carrier chrominance signal separated from the color video signal is frequency-converted into a low frequency range, and the frequency modulated luminance signal and the frequency converted carrier chrominance signal are frequency-division-multiplexed and recorded on and reproduced from the tape. In the present specification, such a recording and reproducing system in which the carrier chrominance signal is frequency-converted into the low frequency range will be referred to as a low-band conversion system. Further, in the VTR for home use, the tape utilization efficiency is improved by employing a system which does not form guard bands at the time of the recording and uses rotary heads having gaps of mutually different azimuth angles to record two mutually adjacent tracks.
On the other hand, in the VTR for business use such as broadcasting and especially in the case of a one-body type VTR having a camera unitarily built therein, there are demands to downsize the apparatus, reduce the weight of the apparatus and obtain a reproduced color video signal having a high picture quality. Hence, the luminance signal and color difference signals are recorded on independent tracks on the tape which has a width identical to that used in the VTR for home use by rotary heads so that a guard band is formed between two mutually adjacent tracks. In the present specification, such a recording and reproducing system will be referred to as a Y/C separation system.
According to the VTR employing the Y/C separation system, during a time period in which one rotary head records one field of the luminance signal on one track, another rotary head records one field of the color difference signals on another track. Thus, two tracks are simultaneously formed in each time period of one field. The track recorded with the luminance signal and the track recorded with the color difference signals are formed adjacent to each other along a longitudinal direction of the tape.
The luminance signal and the color difference signals are recorded on and reproduced from independent tracks on the tape according to the Y/ C separation system. For this reason, although a moire occurs in the case of the VTR employing the low-band conversion system when the frequency modulated luminance signal and the frequency converted carrier chrominance signal are simultaneously recorded on the same track on the tape which is a non-linear transmission system, such a moire will not occur according to the VTR employing the Y/C separation system. In addition, it is possible to reserve sufficiently wide frequency bands for recording and reproducing the luminance signal and the color difference signals. Further, because the VTR employing the Y/C separation system does not record the frequency converted carrier chrominance signal by using the frequency modulated luminance signal as a bias signal, it is possible to improve the signal-to- noise (S/N) ratio of the reproduced color difference signals. As a result, it is possible to obtain a reproduced color video signal having a high picture quality compared to the VTR employing the low-band conversion system.
However, the tape utilization efficiency is poor according to the Y/C separation system because of the need to provide the guard band. Moreover, in the case where the rotary head crosses a guard band at the time of the reproduction and scans a track which is adjacent to the track which is actually to be scanned, the rotary head which should reproduce the luminance signal (or the color difference signals) will reproduce the color difference signals (or the luminance signal) since two mutually adjacent tracks are independently recorded with the luminance signal and the color difference signals. There is no field correlation between the reproduced signals from the two mutually adjacent tracks, and thus, it is impossible to eliminate the crosstalk by a crosstalk cancelling method which uses the field correlation as is done in the VTR for home use which employs the low-band conversion system. Hence, the VTR employing the Y/C separation system has a problem in that the crosstalk is conspicuous in the reproduced picture.
The conventional VTR employing the Y/C separation system simultaneously records and reproduces the luminance signal and the color difference signals on and from independent tracks on the tape by a pair of rotary heads having gaps of mutually different azimuth angles. For this reason, when a tracking error occurs at the time of the reproduction, there is a problem in that a time difference occurs between the reproduced luminance signal and the reproduced color difference signals from the pair of rotary heads.
Accordingly, in order to eliminate the problems described above, recording and reproducing apparatuses were previously proposed in a Japanese Utility Model Application No. 57-66496 (Japanese Laid-Open Utility Model Application No. 58-170012), Japanese Patent Application No. 60-35827 and Japanese Patent Application No. 60-35828 in which the applicant is the same as the applicant of the present application. According to the previously proposed apparatuses, three kinds of signals constituting the color video signal are recorded on and reproduced from a plurality of tracks which are formed in recording regions of the tape which are separated from each other in the tape width direction. Since the recording regions in which the plurality of tracks are simultaneously and independently formed on the tape are completely separated from each other, it is possible to prevent mutual interference among the reproduced signals from the tracks in the different recording regions and hence eliminate the problems of the conventional apparatus.
However, in the previously proposed apparatuses, there is a question as to which tracks the three kinds of signals constituting the color video signal, that is, the luminance signal and two kinds of color difference signals, for example, should be recorded. In other words, the reproduced signals from the tracks in the recording regions which are separated from each other in the tape width direction include time base deviations (jitters) which are mutually different. Generally, the tape is moved in a state where the lower part of the tape is stably guided by a tape guide. Accordingly, there is less jitter in the reproduced signals from the tracks in the lower part of the tape compared to the reproduced signals from the tracks in the upper part of the tape.
The tape is wrapped around the outer peripheral surfaces of an upper rotary drum and a lower stationary drum in a state where the lower part of the tape is guided along the tape guide which is formed on the lower stationary drum. For example, a pair of rotary heads which are mounted on the upper rotary drum at positions separated from each other in the axial direction of the upper rotary drum simultaneously form two independent tracks which are mutually separated in the tape width direction. In this case, in a vicinity of an entrance position of the upper rotary drum where the pair of rotary heads start to make sliding contact with the tape, it is known that the thickness of an air film which is formed between the tape and the outer peripheral surface of the upper rotary drum is larger toward the upper part of the tape and is largest at the upper edge of the tape. For this reason, the contact pressure with which the rotary head makes contact with the tape and the S/N ratio of the signal which is recorded and reproduced are poor in the tracks which are located close to the upper edge of the tape.
On the other hand, when the luminance signal and the two kinds of colour difference signals are compared, the frequency band of the luminance is the widest and the colour difference signals have narrower frequency bands. Further, high frequency components (information related to a small area in the picture) of the colour difference signals are not transmitted as much as a high frequency component of the luminance signal. For this reason, even when there is slight jitter in the colour difference signals, the effects of such slight jitter in the colour difference signals are visually inconspicuous compared to a jitter in the luminance signal. In addition, the luminance signal includes synchronising signals which are used in a servo system and a monitor, and it is desirable for the luminance signal to be free of jitter.
Moreover, in the previously proposed apparatuses, the reproduced signals which are simultaneously obtained from the independent tracks in the recording regions which are separated from each other in the tape width direction include jitters which are mutually different due to an inconsistency in the tension of the tape, a stretch in the tape and the like. However, it is extremely difficult to make the time bases of each of the reproduced signals perfectly coincide with each other.
DE-A1-3 307 324 discloses a helical scan type magnetic recording and reproducing apparatus comprising a rotary body wrapped with a magnetic tape on an outer peripheral surface thereof over a predetermined angular range. The rotary body has a tape guide for guiding a part of the magnetic tape, and n pairs of rotary heads mounted on the rotary body, where n is an integer greater than or equal to two. Each pair of the n pairs of rotary heads is constituted by two rotary heads, which are mounted at mutually opposite positions on a rotational plane of the rotary body at the same height position. Each pair out of the n pairs of rotary heads is mounted at different positions in an axial direction of said rotary body. The n pairs of rotary heads record a luminance signal and two kinds of signals constituting a colour video signal on the magnetic tape.
In DE-A1-3 307 324, page 4, lines 27-30 suggest recording on one recording region of the track a luminance signal and recording on the other recording region a chrominance signal. Page 7, lines 29-32 disclose providing more than two pairs of rotating heads and recording more than two separate recording sections on the track.
DE-A1-3 307 324 further discloses or implies first recording means for recording the luminance signal on one group of tracks out of the first through n-th groups of tracks by supplying the luminance signal to one pair of rotary heads for forming the one group of tracks. The second recording means record at least the two kinds of signals with a predetermined signal format on remaining n-1 groups of tracks excluding the one group of tracks by supplying at least said two kinds of signals to n-1 pairs of rotary heads for forming the remaining n-1 groups of tracks. A luminance signal reproducing circuit reproduces a signal reproduced from the one group of tracks by the one pair of rotary heads into the original luminance signal and reproducing circuit means reproduces the two kinds of signals from the signals reproduced from the remaining n-1 groups of tracks by the remaining n-1 pairs of rotary heads.
A similar apparatus of helical scan type magnetic recording and reproducing is disclosed in US-A-4 296 430. This apparatus has likewise first and second recording means for recording a luminance and a chrominance signal.
According to the invention, there is provided a recording and reproducing apparatus as defined in the appended Claim 1.
Preferred embodiments of the invention are defined in the other appended claims.
It is thus possible to provide a novel and useful helical scan type magnetic recording and reproducing apparatus in which the problems described heretofore are eliminated.
It is also possible to provide a helical scan type magnetic recording and reproducing apparatus in which signals are simultaneously recorded on a plurality of independent tracks which are mutually separated in the tape width direction and a luminance signal is recorded on one track which is closestto a tape guide of a stationary drum. A time base deviation in the luminance signal which is reproduced from the one track is smallest out of the signals reproduced from other tracks due to the provision of the tape guide which stably guides the lower part of the moving tape. Moreover, because the thickness of an air formed between the tape and the outer peripheral surface of the drum is a minimum at the lower part of the tape where the one track is formed, a rotary head makes stable contact with the tape and it is thus possible to perform a satisfactory reproduction. The time base deviation in synchronising signals and the like within the luminance signal which is reproduced from the one track is therefore kept to a minimum, and it is hence possible to stably obtain a reproduced colour picture having a high picture quality.
It is further possible to provide a helical scan type magnetic recording and reproducing apparatus in which out of signals simultaneously recorded on a plurality of independent tracks which are mutually separated in the tape width direction a signal originally not having horizontal synchronising signals is added with synchronising signals before being recorded. At the time of a reproduction, the added synchronising signals are detected and separated from the reproduced signals, and an error signal is obtained by compar- ingthe phase of the reproduced added synchronising signals and the phase of the reproduced horizontal synchronising signals. Mutual time differences among the reproduced signals from the tracks are minimised based on the error signal. Even in the case where the reproduced signals simultaneously obtained from the independent tracks which are separated from each other in the tape width direction include jitters which are mutually different due to an inconsistency in the tension of the tape, a stretch in the tape and the like, it is possible to automatically match the timings (phases) of the reproduced signals. Therefore, it is possible to record and reproduce a colour video signal having a high picture quality.
It is also possible to provide a multiple-function helical scan type magnetic recording and reproducing apparatus in which signals are simultaneously recorded on and reproduced from a plurality of independent tracks which are mutually separated in the tape width direction and the signal to be recorded is obtained by arbitrarily switching a plurality of recording and reproducing circuit systems. In addition to the function of obtaining a reproduced colour video signal having a high picture quality from three kinds of signals which are simultaneously reproduced from the plurality of independent tracks, there is a function of recording on and reproducing from at least one track out of the plurality of independent tracks a different information signal. This different information signal is different from the signals recorded on and reproduced from the remaining tracks, and this different information signal is recorded on (or reproduced from) the at least one track simultaneously as the signals which are recorded on (or reproduced from) the remaining tracks. For example, it is possible to simultaneously record (or reproduce) colour video signals related to a plurality of mutually different television programmes on the plurality of tracks. Hence, a luminance signal picked up by a television camera may be recorded on a certain track with a high picture quality while a colour video signal related to a television programme is recorded on other tracks, for example. As a result, it is possible to use the apparatus in an extremely wide range of applications.
The present invention will be further described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a system block diagram showing a recording system of a recording and reproducing apparatus constituting a preferred embodiment of the invention;
Figures 2A and 2B show frequency spectrums of signals at points of the system shown in Figure 1;
Figures 3A and 3B are a front view and a plan view respectively showing a first arrangement of a positional relationship of rotary heads which may be applied to recording and reproducing apparatus according to the present invention;
Figure 4 is a side view showing a state of contact between a magnetic tape and the rotary heads which may be applied to recording and reproducing apparatus according to the present invention;
Figure 5 shows a first arrangement of a track pattern which is formed on the magnetic tape by recording and reproducing apparatus according to the present invention;
Figure 6 shows a part of the track pattern shown in Figure 5 on an enlarged scale; and
Figure 7 is a system block diagram showing a reproducing system of the recording and reproducing apparatus constituting a preferred embodiment of the invention.

In Figure 1, primary colour signals of red (R), green (G) and blue (B) are respectively applied to input terminals 11, 12 and 13 and are converted into a luminance signal and two kinds of colour difference signals (for example, colour difference signals R-Y and B-Y) in an encoder 14. The luminance signal from the encoder 14 is passed through an automatic gain control (AGC) circuit 15, a lowpass filter 16, an emphasis circuit 17 and a white-dark clipping circuit 18, and is supplied to a frequency modulator 19. On the other hand, the two kinds of colour difference signals R-Y and B-Y from the encoder 14 are passed through respective AGC circuits 20 and 21, lowpass filters 22 and 23, emphasis circuits 24 and 25 and white- dark clipping circuits 26 and 27, and are supplied to respective frequency modulators 28 and 29.
A frequency modulated (FM) luminance signal having a carrier deviation band I of 5 to 6 MHz and a lower sideband II as shown in Figure 2(A) is obtained from the frequency modulator 19. This FM luminance signal is passed through a highpass filter 30 and via a switch 203 to a recording amplifier 33. On the other hand, first and second FM colour difference signals are respectively obtained from the frequency modulators 28 and 29. In Figure 2(B), a frequency spectrum of the first FM colour difference signal which is obtained by frequency-modulating a first carrier by the colour difference signal R-Y is indicated by III, and the first FM colour difference signal has a carrier deviation band IIlc of 5 to 6 MHz. On the other hand, a frequency spectrum of the second FM colour difference signal which is obtained by frequency-modulating a second carrier by the colour difference signal B-Y is indicated by IV, and the first FM colour difference signal has a carrier deviation band IVc of 0.8 to 1.2 MHz. The first and second FM colour difference signals respectively obtained from the frequency modulators 28 and 29 are passed through respective bandpass filters 31 and 32 and are supplied to a mixing circuit 204 wherein the signals are frequency division-multiplexed.
A composite colour video signal applied to an input terminal 185 is subjected to a signal processing similar to the low-band conversion processing performed in a VTR for home use at the time of the recording, for example, and is converted into a second frequency division multiplexed signal in a recording colour video signal processing circuit 186 which processes the signal to be recorded. On the other hand, a composite colour video signal applied to an input terminal 187 is subjected to a low-band conversion processing and is converted into a third frequency division multiplexed signal in a recording colour video signal processing circuit 188 which processes the signal to be recorded.
The construction of the colour video signal processing circuit 188 is the same as that of the colour video signal processing circuit 186, and thus, description will only be given with respect to the construction of the colour video signal processing circuit 186. The composite colour video signal applied to the input terminal 185 is supplied to an AGC circuit 189 and a bandpass filter 190. The level fluctuation in the composite colour video signal is eliminated in the AGC circuit 189, and a lowpass filter 191 separates the luminance signal from the output composite colour video signal of the AGC circuit 189. The luminance signal from the lowpass filter 191 is passed through an equaliser circuit 192, a clamping circuit 193, an emphasis circuit 194 and a white-dark clipping circuit 195 and is supplied to a frequency modulator 196. An FM luminance obtained from the frequency modulator 196 is supplied to a highpass filter 197 wherein the low frequency component in the frequency band of the frequency converted carrier chrominance signal is sufficiently eliminated, and is thereafter supplied to a mixing circuit 198.
On the other hand, the carrier chrominance signal obtained from the bandpass filter 190 is supplied to an AGC circuit 199 wherein the level fluctuation in the colour burst signal is eliminated. The output carrier chrominance signal of the AGC circuit 199 is frequency converted in a frequency converter 200, and is thereafter supplied to a lowpass filter 201 which obtains only the frequency converted carrier chrominance signal which has been frequency-converted into the low frequency range. The frequency converted carrier chrominance signal from the lowpass filter 201 is passed through a burst emphasis circuit 202 and is supplied to the mixing circuit 198. The mixing circuit 198 frequency-division-multiplexes the FM luminance signal from the highpass filter 197 and the frequency converted carrier chrominance signal from the burst emphasis circuit 202. The second frequency division multiplexed signal obtained from the mixing circuit 198 is supplied to a terminal 203b of the switch 203. The frequency spectrum of the second frequency division multiplexed signal is similar to the frequency spectrum of the signal which is recorded and reproduced on the VTR which employs the low-band conversion system and is known, and for this reason, illustration and description of the frequency spectrum of the second frequency division multiplexed signal will be omitted.
The FM luminance signal which has the frequency spectrum shown in Figure 2(A) and is obtained from the highpass filter 30 is supplied to a terminal 203a of the switch 203. The FM luminance signal or the second frequency division multiplexed signal which is obtained through a common terminal 203c of the switch 203 is passed through the recording amplifier 33 and rotary transformers 34₁ and 34₂ and is supplied to rotary heads Y1 and Y2.
The rotary heads Y1, Y2, C1 and C2 are mounted on an upper rotary drum 53 shown in Figures 3A and 3B. Figures 3A and 3B are a front view and a plan view respectively showing a first arrangement of a positional relationship of rotary heads which may be applied to the recording and reproducing apparatus according to the present invention. A rotary shaft 51 of a motor 50 penetrates a central part of a lower stationary drum 52 and is fixed to a central part of the rotary drum 53 which has a cylindrical shape and is used as a rotary body. Hence, only the rotary drum 53 is rotated by the motor 50. As shown in Figures 3A and 4, a tape guide 54 is provided on the stationary drum 52. A magnetic tape 55, is wrapped around the outer peripheral surfaces of the drums 52 and 53 over an angular range of approximately 180°, and is moved in a state where the lower edge of thetape 55 is guided by the tape guide 54.
As shown in the plan view in Figure 3B, the first and second rotary heads Y1 and Y2 are mounted at mutually opposing positions on a rotational plane of the rotary drum 53, and the third and fourth rotary heads C1 and C2 are also mounted at mutually opposing positions on the rotational plane of the rotary drum 53. As may be seen from Figure 3A, the rotary heads Y1 and Y2 are mounted at the same height position, and the rotary heads C1 and C2 are mounted at the same height position. Further, as may be seen from Figures 3A and 3B, the rotary heads Y1 and C1 are mounted at substantially the same position on the rotational plane but the height positions thereof are different in an axial direction of the rotary drum 53. Similarly, the rotary heads Y2 and C2 are mounted at substantially the same position on the rotational plane but the height positions thereof are different in the axial direction of the rotary drum 53. In addition, the rotary heads Y1, Y2, C1 and C2 have gaps of predetermined azimuth angles. For example, the rotary heads Y1, Y2, C1 and C2 respectively have gaps of azimuth angles of +10°, -10°, +10° and -10° with respect to zero azimuth angle, where a positive angle is taken clockwise from the zero azimuth angle and a negative angle is taken counterclockwise from the zero azimuth angle.
As shown in Figure 4, the thickness of an air film formed between the tape 55 and the outer peripheral surface of the rotary drum 53 in a vicinity of the entrance part of the rotary drum 53 increases in an upward direction away from the tape guide 54.
Next, description will be given with respect to the operation of the block system shown in Figure 1 at the time of the recording. During the first one field, tracks T_Y1 and T_C1 shown in Figure 5 are simultaneously and independently formed on the tape 55 by the respective rotary heads Y1 and C1. During the second one field, tracks T_Y2 and T_C2 shown in Figure 5 are simultaneously and independently formed on the tape 55 by the respective rotary heads Y2 and C2. Similarly thereafter, the pair of rotary heads Y1 and C1 and the pair of rotary heads Y2 and C2 alternately form a pair of tracks for every one field, and tracks T_Y3 and T_C3, Ty₄ and T_C4, T_Y5 and T_cs, ... are successively formed on the tape 55 without guard bands. Out of the tracks formed in two recording regions W1 and W2 on the tape 55, the FM luminance signal having the frequency spectrum shown in Figure 2(a) is recorded on the tracks T_Y1 through Ty_l6 which are formed within the recording region W1 which is closer to the tape guide 54. On the other hand, the frequency division multiplxed signal which comprises the first and second FM colour difference signals and has the frequency spectrum shown in Figure 2(B) is recorded on the tracks T_c1, through T_c16 which are formed within the recording region W2. The tracks are formed with an inclination angle 6. In Figure 5, only sixteen tracks are shown in one recording region, for convenience sake.
As shown in Figure 6 which shows a part of the track pattern shown in Figure 5 on the enlarged scale, the horizontal synchronising signals recorded on the tracks T_Y1 through T_Y16 are aligned in the track width direction. That is, the horizontal synchronising signals are recorded with the so-called H-alignment.
In Figure 5, tracks 56₁, 56₂, 57 and 58 which are formed in a longitudinal direction of the tape 55 are formed by stationary heads which are used exclusively for recording and reproducing signals on and from these tracks. First and second channel audio signals are respectively recorded on the audio tracks 56, and 56₂. A time code for indicating a positional information on the tape 55 is recorded on the time code track 57. Further, a control pulse having a constant period is recorded on the control track 58.
The first and second FM colour difference signals obtained from the respective bandpass filters 31 and 32 are multiplexed in the mixing circuit 204, and an output first frequency division multiplexed signal of the mixing circuit 204 is supplied to a terminal 205a of a switch 205. The switching of the switch 205 is independent of the switching of the switch 203. The switch 205 selectively supplies to the recording amplifier 47 one of the first frequency division multiplexed signal obtained from the terminal 205a and the third frequency division multiplexed signal obtained from a terminal 205b of the switch 205. As a result, the track pattern shown in Figure 5 is formed on the tape.
By connecting the switch 203 to the terminal 203b, it is possible to record the second frequency division multiplexed signal which is obtained by processing in the colour video signal processing circuit 186 the composite colour video signal applied to the input terminal 185. Similarly, by connecting the switch 205 to the terminal 205b, it is possible to record on the tracks T_c1, through T_C16 shown in Figure 5 the third frequency division multiplexed signal which is obtained by processing in the colour video signal processing circuit 188 the composite colour video signal applied to the input terminal 187. Accordingly, in the case where the switch 203 is connected to the terminal 203a and the switch 205 is connected to the terminal 205b, it is possible to record the output luminance signal of the encoder 14 on the tracks T_Y1 through T_Y16 the third frequency division multiplexed signal which is derived from the composite colour video signal applied to the input terminal 187.
Next, description will be given with respect to the construction and operation of a reproducing system which reproduces the recorded signals from the tape 55 having the track pattern shown in Figures 5 and 6. The tracks T_Y1 through T_Y16 on the tape 55 are alternately scanned by the rotary heads Y1 and Y2 for every one field. Reproduced FM luminance signals from the rotary heads Y1 and Y2 are passed through the respective rotary transformers 34₁ and 34₂, and a switching circuit (not shown) converts the reproduced FM luminance signals into a continuous signal. The output continuous signal of this switching circuit is passed through a reproducing preamplifier 60 shown in Figure 7 and is supplied via a switch 210 to a frequency demodulator 61. At the same time, the tracks T_C1 through T_C16 on the tape 55 are alternately scanned by the rotary heads C1 and C2 for every one field. Reproduced frequency division multiplexed signals from the rotary heads C1 and C2 are passed through the respective rotary transformers 48₁ and 48₂, and a switching circuit (not shown) converts the reproduced frequency division multiplexed signals into a continuous signal. The output continuous signal of this switching circuit is passed through a reproducing preamplifier 62 shown in Figure 7 and is supplied via a switch 212 to bandpass filters 63 and 64. The bandpass filters 63 and 64 respectively separate the first and second FM colour deference signals from the output signal of the reproducing preamplifier 62.
A reproduced luminance signal obtained from the frequency demodulator 61 is passed through a lowpass filter 67 and a de-emphasis circuit 68 and is supplied to a decoder 69. On the other hand, the reproduced first FM colour difference signal which is obtained from the bandpass filter 63 and has the frequency spectrum III shown in Figure 2(B) is frequency-demodulated into a reproduced colour difference signal R-Y in a frequency demodulator 70. The reproduced second FM colour difference signal which is obtained from the bandpass filter 64 and has the frequency spectrum IV shown in Figure 2(B) is frequency demodulated into a reproduced colour difference signal B-Y in a frequency demodulator71. The reproduced colour difference signals R-Y and B-Y are respectively passed through lowpass filters 72 and 73 and de-emphasis circuits 74 and 75 and are supplied to the decoder 69. The decoder 69 supplies primary colour signals of red (R), green (G) and blue (B) to respective output terminals 76, 77 and 78.
According to the present embodiment, a time base deviation (jitter) in the reproduced luminance signal from the tracks T_Y1 through T_Y16 in the recording region W1 which is closest to the tape guide 54 caused by the positional deviation as the tape 55 moves is smallest out of the reproduced signals from the tracks T_c1 through T_c16 in the recording region W2 due to the provision of the tape guide 54which stably guides the lower part of the moving tape 55. Moreover, because the thickness of an airfilm formed between the tape 55 and the outer peripheral surfaces of the drums 52 and 53 is a minimum at the lower part of the tape 55 where the recording region W1 exists, the rotary heads Y1 and Y2 make stable contact with the tape 55 and it is thus possible to perform a satisfactory reproduction. The jitter in synchronising signals and the like within the luminance signal which is reproduced from the tracks T_Y1 through Ty_l6 in the recording region W1 is therefore kept to a minimum, and it is hence possible to stably obtain a reproduced colour picture having a high picture quality.
In the case where the FM luminance signal is recorded on the tracks T_Y1 through T_Y16, the switch 210 is connected to a terminal 210a thereof, and the reproduced signal is selectively supplied to the frequency demodulator 61. In the case where the second frequency division multiplexed signal is recorded on the tracks T_Y1 through T_Y16, the switch 210 is connected to a terminal 210b thereof, and the reproduced signal is selectively supplied to a reproduced colour video signal processing circuit 211 for processing the reproduced signal. On the other hand, in the case where the first and second FM luminance signals are recorded on the tracks T_c1 through T_c16, the switch 212 is connected to a terminal 212a thereof, and the reproduced signal is selectively supplied to the bandpass filters 63 and 64. Furthermore, in the case where the third frequency division multiplexed signal comprising the FM luminance signal and the frequency converted carrier chrominance signal is recorded on the tracks T_c1, through T_c16, the switch 212 is connected to a terminal 212b thereof, and the reproduced signal is selectively supplied to a reproduced colour video signal processing circuit 213 for processing the reproduced signal.
The switching of the switch 210 is independent of the switching of the switch 212. When it is assumed that the switches 210 and 212 are respectively connected to the terminals 210b and 212b, the reproduced signals from the rotary heads Y1 and Y2 are supplied to the colour video signal processing circuit 211 and the reproduced signals from the rotary heads C1 and C2 are supplied to the colour video signal processing circuit 213. The colour video signal processing circuits 211 and 213 have the same circuit construction which is known and is similar to that of a reproducing system of the existing VTR which employs the low-band conversion system. Accordingly, description will be given only with respect to the operation of the colour video signal processing circuit211. The reproduced signal from the switch 210 is supplied to a highpass filter 214 wherein the FM luminance signal is separated and to a lowpass filter 215 wherein the frequency converted carrier chrominance signal is separated. The reproduced FM luminance signal obtained from the highpass filter 214 is passed through a dropout compensation circuit 216, a limiter 217 and a frequency demodulator 218 so as to obtain a reproduced luminance signal having no dropouts. The output luminance signal of the frequency demodulator 218 is passed through an equaliser circuit 219 and a de-emphasis circuit 220 and is supplied to a lowpass filter 221.
The reproduced frequency converted carrier chrominance signal obtained from the lowpass filter 215 is passed through an automatic chrominance control (ACC) circuit 222, a frequency converter 223 and a bandpass filter 224 so as to obtain a reproduced carrier chrominance signal which is restored to the original frequency band. The reproduced carrier chrominance signal from the bandpass filter 224 is passed through a burst de-emphasis circuit 225 and is multiplexed with the reproduced luminance signal from the lowpass filter 221 so as to obtain a reproduced composite colour video signal. This reproduced composite colour video signal is outputted through an output terminal 226. Similarly, a reproduced composite colour video signal is obtained from the colour video signal processing circuit 213 and is outputted through an output terminal 227.
An I-signal and a Q-signal may be used as the first and second colour difference signals. Moreover, it is possible to record and reproduce the two kinds of colour difference signals which are time-division-multiplexed instead of being frequency-division-multiplexed.
The signal which is switched over and recorded and reproduced is not limited to the frequency division multiplexed signal of the frequency converted carrier chrominance signal and the FM luminance signal, but may be video signals having other signal formats. In addition, it is possible to record and reproduce an information signal other than the video signal, such as an analog audio signal or a digital audio signal.
The signal which is recorded and reproduced by the rotary heads C1 and C2 simply needs to be a chrominance signal. For example, the signal which is recorded and reproduced by the rotary heads C1 and C2 may be a multiplexed signal of the frequency converted carrier chrominance signal and a bias signal, an FM frequency converted carrier chrominance signal which is obtained by frequency modulating a carrier by the frequency converted carrier chrominance signal, an FM line-sequential colour difference signal, a multiplexed signal of three kinds of FM signals which are obtained by independently frequency modulating the three primary colour signals and the like. Furthermore, the signal which is recorded and reproduced by the rotary heads H1 through H6 simply needs to be the three kinds of signals constituting the colour video signal. Hence, the signal which is recorded and reproduced by the rotary heads H1 through H6 may be three kinds of FM primary colour signals which are obtained by independently frequency-modulating the three primary colour signals. The rotary heads C1, C2, Y1, Y2 and H1 through H6 may be mounted on a rotary body other than the rotary drum described before. For example, the rotary heads may be mounted on a flat rectangular head bar which is arranged in two or three stages. In addition, the rotary heads C1, C2, Y1 and Y2 may have gaps of the same azimuth angle and form a track pattern in which a guard band is provided between mutually adjacent tracks. It is not essential for the azimuth angles of the gaps of the rotary heads Y1 and C1, and the rotary heads Y2 and C2 to be selected to the same azimuth angle.

Claims

1. A helical scan type magnetic recording and reproducing apparatus comprising a rotary body (52, 53) wrapped with a magnetic tape (55) on an outer peripheral surface thereof over a predetermined angular range, said rotary body having a tape guide (54) for guiding a part of the magnetic tape, and n pairs of rotary heads (Y1, Y2, C1, C2) mounted on said rotary body, where n is an integer greater than or equal to two, each pair out of said n pairs of rotary heads being constituted by two rotary heads which are mounted at mutually opposite positions on a rotational plane of said rotary body at the same height position, each pair out of said n pairs of rotary heads being mounted at different positions in an axial direction of said rotary body, said n pairs of rotary heads recording a luminance signal and two kinds of signals constituting a colour video signal on the magnetic tape by simultaneously forming first through nth groups of tracks (T_Y1-T_Y16, T_C1-T_c16) at the time of a recording and simultaneously reproducing the recorded signals from the first through the n-th groups of tracks at the time of a reproduction, said first through n-th groups of tracks being independent of each other and being mutually separated in a width direction of the magnetic tape, there are provided: first recording means (15-19, 30, 33, 34₁, 34₂) for generating and recording said luminance signal on one group of tracks (T_Y1-T_Y16) out of said first through n-th groups of tracks by supplying said luminance signal to a first pair of the end pairs of rotary heads (Y1, Y2) for forming said one group of tracks, second recording means (20-29,31,32,47, 48₁, 48₂) for generating and recording at least said two kinds of signals with a predetermined signal format on remaining n-1 groups of tracks (T_cl-T_C16) by supplying the two kinds of signal to a pair of the end excluding pairs of rotary heads (C1, C2) for forming said remaining n-1 groups of tracks, a luminance signal receiving circuit (61) for receiving a signal reproduced from said one group of tracks by said first pair of rotary heads, receiving circuit means (63, 64, 70, 75) for receiving the signals reproduced from said remaining n-1 groups of tracks by said second pair of the end pairs of rotary heads, characterised in that said one group of tracks are formed on a part of the magnetic tape (55) closest to said part which is guided by said tape guide (54) of said rotary body (52, 53), and that said magnetic recording and reproducing apparatus comprises n recording colour video signal processing circuits (186, 188) each of which separates a luminance signal and a carrier chrominance signal from composite colour video signals inputted thereto, frequency- modulates the separated luminance signal, frequency-converts the separated carrier chrominance signal into a frequency band lower than a frequency band of the frequency modulated luminance signal and generates a frequency division multiplexed signal in which the frequency modulated luminance signal and the frequency converted carrier chrominance signal are frequency-division-multiplexed, said second recording means comprising mixing means (204) for generating a mixed signal by mixing said two kinds of signals; first switching means (203) for selectively supplying to said first pair of rotary heads the output frequency division multiplexed signal of one of said n recording colour video signal processing circuits or said luminance signal from said first recording means; and second switching means (205) for selectively supplying to said second pair of rotary heads output signals of remaining n-1 recording colour video signal processing circuits or said mixed signal generated by said mixing means (204).

2. A magnetic recording and reproducing apparatus as claimed in Claim 1, characterised in that said second recording means (20-29, 31, 32, 35-47, 48₁, 48₂) comprises synchronising signal adding means (106, 145-147) for adding synchronising signals having a constant period to one or both of said two kinds of signals, converting means (108, 109, 111, 22-27, 149-154) for converting a signal format of the two kinds of signals at least one of which is added with the synchronising signals into said predetermined signal format and supplying means (112, 159-162₂) for supplying an output signal of said converting means to said n-1 pairs of rotary heads, said recording and reproducing apparatus further comprising synchronising signal separating means (122, 125, 131, 175, 176) for separating reproduced horizontal synchronising signals and reproduced synchronising signals from signals which are simultaneously reproduced by said first through n-th groups of tracks by said n pairs of rotary heads and time compensation means (129, 135-137, 177, 178) for obtaining a phase error signal by comparing phases of the reproduced horizontal synchronising signals and the reproduced synchronising signals which are separated in said synchronising signal separating means by taking the reproduced horizontal synchronising signals as a reference and for matching timings of the reproduced signals from said first through n-th groups of tracks based on the phase error signal.

3. A magnetic recording and reproducing apparatus as claimed in Claim 2, characterised in that said time compensation means (129,135-137, 177, 178) comprises charge transfer elements (129, 135) independently supplied with the two kinds of signals which are obtained by demodulating the signals reproduced by said n-1 pairs of rotary heads, phase comparator means (136, 177) for comparing the phases of the reproduced horizontal synchronising signal and the reproduced synchronising signals and variable frequency oscillator means (137, 178) variably controlled of an oscillation frequency of an output signal thereof responsive to an output error signal of said phase comparator means for variably controlling delay times of said charge transfer elements by supplying the output signal of said variable frequency oscillator to said charge transfer elements as a clock pulse.

4. A magnetic recording and reproducing apparatus as claimed in Claim 2, characterised in that said two kinds of signals are two kinds of colour difference signals, said synchronising signal adding means (106, 145-147) comprising a synchronising signal generator (106-147) for generating synchronising signals having a period which is identical to that of the horizontal synchronising signals and having a phase which is approximately the same as that of the horizontal synchronising signals and means (145, 146) for adding the synchronising signals from said synchronising signal generating means to at least one of said two kinds of colour difference signals.

5. A magnetic recording and reproducing apparatus as claimed in Claim 1, characterised in that each pair of said n pairs of rotary heads (Y1, Y2, C1, C2, H1-H6) is constituted by two rotary heads which have gaps of mutually different azimuth angles, said n pairs of rotary heads being aligned in the axial direction of said rotary body.

6. A magnetic recording and reproducing apparatus as claimed in Claim 1, characterised in that n is equal to two, said second recording means (20-29, 31, 32, 35-47, 48₁, 48₂) comprising modulating means (28, 29, 108, 109) for independently frequency-modulating the two kinds of signals into two kinds of frequency modulated colour difference signals having different frequency bands and mixing means (35,111,204) for producing a frequency division multiplexed signal at least including said two kinds of frequency modulated colour difference signals, said mixing means supplying the output frequency division multiplexed signal thereof to one of two pairs of rotary heads.

7. A magnetic recording and reproducing apparatus as claimed in Claim 1, characterised in that n is equal to three, said second recording , means (20-29, 31, 32, 35-47, 48₁, 48₂) comprising modulating means (149, 150) for independently frequency-modulating the two kinds of signals into first and second frequency modulated colour difference signals and mixing means (153, 154) for producing a first frequency division multiplexed signal at least including said first frequency modulated colour difference signal and a second frequency division multiplexed signal at least including said second frequency modulated colour difference signal, said mixing means independently supplying the output first and second frequency division multiplexed signals thereof to two of three pairs of rotary heads.